Forest

Forest Zone

The climatic diversity in Iran has given rise to five distinct and important forest zones:
1)   Hyrcanian Forest Zone
2)   Arasbaran Forest Zone
3)   Zagros Forest Zone
4)   Iran-o-Tourani Forest Zone
5)   Persian Gulf and Sea of Oman Forest Zone

1- Hyrcanian Forest Zone:
The Hyrcanian forests are remnants of the Tertiary period (Geological Era) and are recognized as one of the oldest forests in the world. These forests are listed as a World Natural Heritage site, and a portion of them was inscribed as a UNESCO World Heritage site in 2019.
These forests stretch like a green belt across the northern slopes of the Alborz Mountains in northern Iran, covering the southern shores of the Caspian Sea. The approximate length of this region is 800 kilometers, and its width ranges between 20 to 70 kilometers, covering an area of about 2.4 million hectares. The Hyrcanian forests extend from sea level up to an altitude of about 2,800 meters. The climate of this region is temperate and humid, with annual rainfall ranging between 600 and 2,000 mm.
The Hyrcanian forests are considered one of the richest forests in the world in terms of flora and bear a strong resemblance to the broadleaf forests of Central Europe. However, with over 80 native woody species (tree and shrub species), they are significantly richer. Another notable feature of the Hyrcanian region is the presence of epiphytic plants, particularly hanging mosses, which can be attributed to the high humidity in the area. The presence of broadleaf species is abundant in this region, forming diverse forest types, but it is relatively poor in coniferous species.
The indicator trees in the Hyrcanian forests include:
Cappadocian maple (Acer cappadocicum), velvet maple (Acer velutinum), Persian silk tree (Albizia julibrissin), Caucasian alder (Alnus subcordata), Hyrcanian boxwood (Buxus hyrcana), European hornbeam (Carpinus betulus), wild cherry (Cerasus avium), Mediterranean cypress (Cupressus sempervirens), date-plum (Diospyros lotus), Oriental beech (Fagus orientalis), European ash (Fraxinus excelsior), Caspian locust (Gleditsia caspica), Persian ironwood (Parrotia persica), Caspian poplar (Populus caspica), Caucasian wingnut (Pterocarya fraxinifolia), chestnut-leaved oak (Quercus castaneifolia), wild service tree (Sorbus torminalis), English yew (Taxus baccata), Oriental arborvitae (Thuja orientalis), Caucasian lime (Tilia begonifolia), wych elm (Ulmus glabra), and Caucasian elm (Zelkova carpinifolia).
Species such as Parrotia persica, Quercus castaneifolia, Pterocarya fraxinifolia, Gleditsia caspica, Zelkova carpinifolia, and Populus caspica are commonly found in these forests and are considered remnants of the Tertiary period.

The main forest communities along the altitudinal gradient of the Hyrcanian forests include:
- Lowland communities: Querco-Buxetum, Pterocaryo-Alnetum
- Lower montane communities: Querco-Carpinetum, Zelkovo-Quercetum, Parrotio-Carpinetum
- Mid-montane community: Fagetum hyrcanum
- Upper montane communities: Carpinetum orientale, Quercetum macranthera, Querco-Carpinetum orientalis

2- Arasbaran Forest Zone
The Arasbaran forest zone is located in northwestern Iran, within the watershed of the Aras River (near the borders of Iran with Azerbaijan and Armenia), covering an area of approximately 160,000 hectares. This region is recognized as one of the most important genetic reserves in Iran and the world. Due to its unique climatic conditions, high biodiversity, and the presence of rare plant and animal species, a portion of the Arasbaran region was designated as a UNESCO Biosphere Reserve in 1976. The semi-humid climate has facilitated the establishment of semi-dense forests in this area. The annual rainfall ranges between 300 and 600 mm, but the high number of foggy days has played a significant role in increasing moisture and enriching the vegetation cover.

Despite the small area of the Arasbaran forests, approximately 1,072 plant species and 97 woody species have been identified in this region. The most important woody plants in this region include:
- Caucasian oak (Quercus macranthera)
- Sessile oak (Quercus petraea)
- European hornbeam (Carpinus betulus)
- Field maple (Acer campestre)
- Montpellier maple (Acer monspessulanum)
- Hyrcanian maple (Acer hyrcanum)
- Stinking juniper (Juniperus foetidissima)
- English yew (Taxus baccata)
- Wild pistacio (Pistacia atlantica)
- Christ's-thorn (Paliurus spina-christi)
- Wild service tree (Sorbus torminalis)
- Wych elm (Ulmus glabra)
- Smoke tree (Cotinus coggygria)
- Wayfaring tree (Viburnum lantana)
- Cornelian cherry (Cornus mas).

The region is topographically diverse, with elevations ranging from 250 meters to over 2,200 meters above sea level. The best-preserved forests of Arasbaran are found at elevations between 1,000 and 1,700 meters, as forests at higher and lower elevations have been severely degraded. The forest form is primarily either coppice or seed-origin, with coppice being dominant in most areas. The main forest types in the Arasbaran region consist of three species: Quercus macranthera, Quercus petraea, and Carpinus betulus. In some areas, pure or mixed stands of coniferous species are also observed. The notable conifers in Arasbaran include Taxus baccata, Juniperus foetidissima, and Juniperus communis.
This region is also rich in faunal biodiversity and is the habitat of one of the world's rarest birds, the Caucasian grouse.

3- Zagros Forest Zone
The Zagros forest zone covers a vast area of the Zagros mountain range, stretching 1,600 kilometers from northwestern to southeastern Iran, near the Strait of Hormuz. The forests in this region cover an area of approximately 5.5 million hectares. These forests play a crucial role in water supply, soil conservation, climate regulation, biodiversity preservation, agricultural and livestock production, and providing environmental benefits at the national level. The climate of this region is predominantly semi-arid to Mediterranean, with annual rainfall ranging between 300 and 800 mm.

The Zagros forests are home to over 180 tree and shrub species, highlighting their high genetic value. Since the Brant's oak is the dominant species in these forests, the Zagros forests are primarily known as oak forests. Some of the most important tree and shrub species in the Zagros region include:
- Brant's oak (Quercus brantii)
- Aleppo oak (Quercus infectoria)
- Lebanon oak (Quercus libani)
- Montpellier maple (Acer monspesulanum)
- Wild pistacio (Pistacia atlantica)
- Khinjuk (Pistacia khinjuk)
- Wild almond (Amygdalus scoparia)
- Caucasian hackberry (Celtis caucasica)
- Daphne (Daphne sp.)
- Juniper (Juniperus polycarpos)
- Pear (Pyrus sp.).

Due to human-induced degradation, about 90% of the forests in this region have regenerated into a coppice-with-seed-origin form. The limited parts of the Zagros forests with a seed-origin form are generally middle-aged to old-aged. The region is topographically diverse, with elevations ranging from 500 meters to over 4,000 meters above sea level.
The most extensive and significant forest community in the Zagros forests is the Brant's oak community, which spans an elevation range of 1000 to 2000 meters above sea level. At higher elevations, the juniper forest community is found, while at lower elevations, mixed communities of oak, wild almond, pistachio, and Montpellier maple are present.

4- Iran-o- Tourani Forest Zone
The Iran-o-Tourani vegetation region covers a vast area of the central Iranian plateau. This region is one of the most important ecological zones in Iran, playing a significant role in maintaining the balance of the country's ecosystems due to its vast expanse and high diversity of plant and animal species. The area of Iran-o-Tourani forests is estimated to be around 4 million hectares, which, including woodlands and shrublands, reaches approximately 7 million hectares. These forests and wooded lands are considered protected areas, and their primary role is to conserve water and soil resources. The climate of this region is arid to semi-arid, with annual rainfall ranging between 50 and 250 mm. Low precipitation and a long dry season distinguish this region from other parts of the country. The climatic conditions of this region have led to the formation of plant communities adapted to water scarcity. This vegetation plays a key role in combating desertification in the area by stabilizing the soil and preventing wind and water erosion. The forests here include drought-resistant species such as wild pistachio, wild almond, juniper, and tamarisk.
The Iran-o-Tourani region is topographically diverse, with elevations ranging from 500 meters to over 3,000 meters above sea level. Due to the region's vastness and climatic variations, the forests of the Iran-o-Tourani zone are divided into two main types: mountainous and plains forests. Mountainous forest communities are typically found at elevations above 1,500 meters.
Some of the most important forest communities in this region include:
1) Plains section: Desert forest types including saxaul (Haloxlon sp.), tamarisk (Tamarix sp.), beancaper (Zygophyllum sp.), and fire bush (Calligonum sp.).
2) Mountainous section: Mountain forest types include juniper (Juniperus polycarpos), pistachio (Pistacia atlantica), and almond (Amygdalus sp.).

5-Persian Gulf and Sea of Oman forest Zone
The vegetation zone of the Persian Gulf and the Sea of Oman covers a narrow strip encompassing part of the southwestern and the entire southern coast of Iran up to the border with Pakistan. The elevation range of this region extends from sea level to about 200 meters above sea level. The forest area of this region is estimated to be approximately 2.6 million hectares. The average annual rainfall in this area varies between 100 and 250 mm.
The main vegetation elements of the region generally belong to subtropical areas, and the most important tree and shrub species in this region include: babul (Acacia nilotica), oerfota acacia (Acacia oerfota), salam (Acacia ehrenbergia), Persian mesquite (Prosopis cineraria), Euphrates poplar (Popolus euphratica), lebbek tree (Albizia lebbeck), karira (Capparis deciua), Arabian moringa (Moringa peregrina), Sodom apple (Calotropis procera), oleander (Nerium sp.), toothbrush tree (Salvadora persica), desert teak (Tecomella undulata), grey mangrove (Avicennia marina), and loop-root mangrove (Rhizophora mucronata).
Due to ecological differences, the main vegetation cover of this region is divided into two domains: the Persian Gulf and the Sea of Oman. Among the indicator species of the Persian Gulf domain are Christ's thorn jujube (Ziziphus spina-christi), Persian mesquite (Prosopis cineraria), and Euphrates poplar (Popolus euphratica). The Sea of Oman domain is richer in vegetation, and its indicator species include the Persian mesquite (Prosopis cineraria) and various acacias (Acacia spp.). In the eastern part of this domain, the Mazari palm (Nannorrhops ritchiana) is also observed. These forests are also referred to as semi-savanna forests.
In parts of this region, valuable mangrove forests are also distributed, stretching along the coasts of the Persian Gulf and the Sea of Oman. The majority of mangrove forests in Iran consist of the gray mangrove (Avicennia marina), with the loop-root mangrove (Rhizophora mucronata) found in limited areas. Since these forests host a diverse range of fish, birds, and aquatic species, they hold significant importance in terms of biodiversity. Additionally, these forests are recognized as one of the most efficient ecosystems in carbon sequestration and storage, playing a crucial role in reducing greenhouse gases.

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